This invention relates to an ultrasonic seam welding apparatus for seam welding workpieces of sheet state, which are piled in plurality one above the other for being held in forced contact between a horn coupled to an ultrasonic resonator and a presser roller, by means of feeding the workpieces while imparting the same ultrasonic oscillation.
As an apparatus in this category U.S. Pat. No. 3,734,805 discloses one in which workpieces are held in forced contact between a working surface formed on top of a horn oscillating in a longitudinal direction thereof and the external peripheral surface of a driven feed roller for being seam welded while being fed by the rotation of the roller. In this apparatus heat naturally generated by the compressive force repeatedly applied on the workpieces by the horn advantageously enhances the energy efficiency. Another advantage of this type apparatus is that no load in a lateral direction is applied to a horn assembly including the horn therein. An inherent weak point of this apparatus lies however in that some pieces of the piled workpieces forced to the horn are relatively inferior in the feeding to those on the opposite side, which is liable to produce wrinkles in the welded portion. U.S. Pat. No. 3,955,740 discloses on the other hand an apparatus, wherein a horn having a large diametered portion in it is parallely disposed to the rotational axis of an anvil wheel roller for being rotated so that workpieces are held in forced contact between the external peripheral surface of the large diametered portion of the horn and the external peripheral surface of the anvil wheel to be seam welded. This type apparatus is disadvantageous in that the energy efficiency is inferior to a case where the horn is perpendicularly contacted to workpieces because of the oscillating direction of the working surface of the horn, i.e., the external peripheral surface of the large diametered portion of the horn, in this case being parallel to the workpieces under the process, while good feeding effect is being advantageously ensured by the light and smooth following rotation of the anvil wheel to the workpieces which are fed by the horn. A further disclosure can be seen in the U.S. Pat. No. 3,955,740, in which the axial oscillation of the horn is converted at the large diametered portion thereof to the radial direction before being transmitted to the workpieces. Even in this instance the energy efficiency is inevitably deteriorated in the course of the direction converting of the oscillation. In addition to the above, the horn is obliged to be under a power in the perpendicular direction to the axis of the horn for holding the workpieces inbetween with the anvil wheel, which necessitates (1) the build-up of the horn assembly supporting means to be solid and stout and (2) to disadvantageously narrow the bosom or depth of the processing area, that is the distance of the actual processing place away from the column of the machine frame, because the horn is hard to be projected from the machine frame very long due to its cantilever structure.